This invention is generally directed to toner compositions, and more specifically, the present invention is directed to developer compositions and toner compositions having incorporated therein specific additives. More specifically, the present invention relates to the incorporation into toner compositions of specific oxides prepared by a precipitation process rather than the flame hydrolysis methods of the prior art. These toner compositions, which have improved admix properties, excellent flow characteristics, superior developability, and humidity insensitivity enable their use in xerographic imaging, and printing processes.
Toner compositions with additives therein are known. There is described, for example in U.S. Pat. No. 3,983,045, toner compositions having incorporated therein additives of silicon dioxide, and metal salts of a fatty acid. According to the teachings of this patent, the silica particles are added for the purpose of cleaning the imaging member thus preventing lubricants such as zinc stearate from adhering thereto. The silicon oxide particles utilized are prepared by a flame hydrolysis process resulting in material of a diameter of from about 10 to about 30 millimicrons. These particles are spherical in shape, however, they are sintered together causing chains and aggregates to form. Accordingly, the resulting particles are difficult to disperse in the toner compositions; and further, they are, in many instances, humidity sensitive. Also, the silica particles prepared by the flame hydrolysis method have a tendency to adhere to the surface of carrier particles thereby resulting in undesirable charge polarity of the wrong sign to be generated on the toner particles. Therefore, developer compositions with these additives therein can generate low optical density images, high image background deposits, and low toner concentration latitudes at certain relative humidities. These problems are eliminated with the toner compositions of the present invention.
Additionally, disclosed in U.S. Pat. No. 3,320,169 is a developer composition comprised of three components, namely magnetic carrier particles, and toner particles consisting of a discrete mixture of pigmented resin particles in an aliphatic acid having from about 10 to 26 carbon atoms, and/or salts of such aliphatic acids. Examples of fatty acids disclosed include saturated or unsaturated acids with from 10 to 26 carbon atoms such as lauric, stearic, oleic, and the like. It is known that other additives, including colloidal silicas, can be included in these toner compositions.
Furthermore, described in U.S. Pat. No. 3,900,588 are developer compositions comprised of toner resin particles and a dual additive of a substantially smearless polymeric additive in a finely divided abrasive material. Examples of smearless polymeric substances that may be selected include polyvinylidene fluoride, and other similar polymers, reference the disclosure in column 5, beginning at line 51. Abrasive materials that may be selected for incorporation into the toner composition of the '588 patent include colloidal silicas, reference the disclosure in column 7, beginning at around line 11. It is further indicated in this patent that the particle size of the abrasive additive should be from about 1 to about 50 millimicrons, and preferably between about 10 to about 100 millimicrons. Additionally, the use of hydrophobic silica particles in affecting the dispersion polymerization of toner compositions is disclosed in U.S. Pat. No. 4,345,015. Other patents disclosing the use of silicas in toner compositions, which silicas are prepared by a flame hydrolysis process, are U.S. Pat. Nos. 4,301,228; 4,288,516; and 4,395,485.
Moreover, there is described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica compositions. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition with a positively charged triboelectric relationship with respect to the colloidal silica.
Additionally, there is disclosed in U.S. Pat. No. 4,298,671 positively charged toner compositions with resin particles and pigment particles, and as a charge enhancing additive alkyl pyridinium compounds and their hydrates of the formula as detailed in column 3, beginning at line 14. Examples of alkyl pyridinium compounds disclosed include cetyl pyridinium chloride. These toner compositions can have incorporated therein additive particles of silicon oxide prepared by the flame hydrolysis process.
There is also disclosed in a copending application developer compositions comprised of a mixture of resin particles, additive particles of silica oxides, additive particles of a metal salt of a fatty acid, and uncoated ferrite carrier particles. The silica particles selected for this developer composition are prepared by a flame hydrolysis process, therefore, difficulties can be encountered in dispersing these particles in toner resin compositions.
These prior art toner compositions in some instances possess narrow toner concentration latitudes; high concentration of wrong sign toner particles; slow admix properties; developed images with high background; and undesirable humidity sensitivity, problems overcome with the toner; and developer compositions of the present invention.